Demonstration of all-optical Mach-Zehnder demultiplexer

Recently, Kang et al. reported the demonstration of an all-optical Mach-Zehnder demultiplexer (see ibid., vol.31, no.9, pp.749-50, 1995). In their paper, Kang et al. drew what we believe is an invalid comparison with work previously published by ourselves (see S. Nakamura et al., Appl. Phys. Lett., vol.65, no.3, pp.283-5, 1994). They described the device proposed by us, the symmetric Mach-Zehnder (SMZ) all-optical switch, as a Mach-Zehnder version of the terahertz optical asymmetric demultiplexer (TOAD). The SMZ and TOAD are in fact different independently-developed devices, each of which has its advantages and disadvantages. A reply by Kang et al. to this comment is included.